A carbon dot-based tracer type scale inhibitor and a preparation method and application thereof

Abstract

The application belongs to the field of chemical synthesis, and relates to preparation of carbon dots and polymers, in particular to a kind of tracing type scale inhibitor based on carbon dots and its preparation method and application. Amino trimethylene phosphonic acid (ATMP) and sodium citrate are used as precursors, carbon dots (CDs) with high fluorescence intensity and stability are synthesized by one-step hydrothermal method, and the CDs are polymerized with acrylic acid (AA) to obtain polyacrylic acid (PAA) traced by CDs. The CDs have good biocompatibility, strong fluorescence intensity and are less affected by environmental factors, and are a suitable choice for tracers. The CDs are polymerized with AA by polymerization method, the fluorescence intensity of the composite PAA@CDs presents a good linear relationship with the concentration, and quantitative detection of PAA is realized. The tracing type scale inhibitor based on carbon dots synthesized by the application has simple preparation process and good performance, not only explores the potential application of CDs in water treatment direction, but also provides a new idea for detection of scale inhibitor concentration.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis and relates to the preparation of carbon dots, specifically a carbon dot-based tracer scale inhibitor, its preparation method, and its application. Background Technology

[0002] During the operation of industrial circulating cooling water, inorganic salt scale ions (Ca) form scale. 2+ Mg 2+ HCO 3- As water concentration increases and water temperature rises, the concentration of scale inhibitors (such as calcium carbonate, sodium carbonate, and sodium carbonate) forms dense scale, which is regularly deposited on the pipe walls, significantly impacting production load. Selecting the appropriate water treatment agent is a prerequisite for ensuring the normal operation of the circulating cooling water system, and controlling the concentration of the scale inhibitor is a key technology to ensure its optimal efficacy. In actual production, the agent used needs to be added to the circulating water system in precise quantities, and the dosage needs to be adjusted promptly according to changes in water quality conditions. Therefore, accurately and quickly detecting the real-time concentration of the water treatment agent is essential.

[0003] Currently, in industry, the content of scale inhibitors is mainly determined by ammonium molybdate spectrophotometry and indirect detection of calcium ion concentration, requiring specialized instruments (publication number CN1506325A). The ammonium molybdate spectrophotometric method determines the concentration of the treatment agent by detecting the total phosphorus content. However, phosphorus-containing scale inhibitors are gradually being phased out due to environmental pollution problems, and the ammonium molybdate spectrophotometric method cannot be applied to the determination of the concentration of phosphorus-free water treatment agents. Furthermore, titration and spectrophotometry methods for determining calcium ion concentrations are also problematic. 2+ Mg 2+ The application of scale inhibitors is limited by complex processes, expensive equipment, or the inability to perform on-site testing. Therefore, there is a need to find accurate, continuous, and convenient methods to detect the concentration of scale inhibitors.

[0004] Fluorescent tracer technology boasts advantages such as high sensitivity, good selectivity, low detection limit, and good controllability, making it a promising application in oilfield development and water treatment. However, traditional fluorescent dyes, such as fluorescein, coumarin, and rhodamine, often require multi-step synthesis and modification to create fluorescent tracer water treatment agents. This process is complex, involves high raw material costs, and suffers from poor environmental performance. Furthermore, the stability of some synthesized water treatment agents does not meet the requirements for use in circulating cooling water systems.

[0005] Carbon dots (CDs) are a class of zero-dimensional carbon nanomaterials with significant fluorescence properties. They possess excellent optical properties, good water solubility, low toxicity, environmental friendliness, wide availability of raw materials, low cost, good biocompatibility, and ease of modification. To further improve the biocompatibility of fluorescent tracer-type scale inhibitors, introducing carbon dots as markers into scale inhibitors to construct fluorescent tracer-type scale inhibitors represents a cutting-edge technology combining nanomaterial preparation, fluorescence detection, and water treatment agents. Application CN112811412A discloses a carbon dot fluorescent tracer, prepared from citric acid and phosphate in a one-step hydrothermal process for tracer and corrosion inhibition in water. However, research on carbon dot tracer-type scale inhibitors is currently scarce. Therefore, developing carbon dots with high and stable fluorescence intensity, exploring the composite mode of carbon dots and scale inhibitors through the selection of suitable scale inhibitors, and ultimately constructing fluorescent tracer-type scale inhibitors to investigate their scale inhibition and tracer properties is of practical significance. This not only breaks through the current limitations of tracers being affected by environmental factors, but also fully leverages the potential of carbon dots in water treatment. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a carbon dot-based tracer scale inhibitor, its preparation method, and its application. The preparation method of the tracer scale inhibitor PAA@CDs prepared in this application is simple, efficient, and easy to implement. The prepared PAA@CDs are less affected by environmental factors, exhibit stable fluorescence intensity, and can be used for the detection of PAA concentration in industrial circulating cooling water.

[0007] The technical solution of this invention is implemented as follows:

[0008] A tracer carbon dot, wherein the carbon dot is a blue light emitting carbon dot, and the fluorescence excitation spectrum and emission spectrum exhibit a good mirror symmetry relationship, with an optimal excitation wavelength of 330 nm and an optimal emission wavelength of 432 nm; the particle size distribution is 0.6~1.8 nm, and the average particle size is 1.15 nm; the surface contains amino and phosphate groups, etc.

[0009] The above-mentioned tracer carbon dots are CDs prepared using aminotrimethylenephosphonic acid (ATMP) and sodium citrate as precursors. The preparation method includes the following steps:

[0010] Sodium citrate was dissolved in ultrapure water and sonicated until dissolved. Then, ATMP solution was added and the mixture was shaken to make a reaction volume of 10 mL. The solution was placed in a high-pressure reactor for high-temperature reaction. After the reaction was completed, the mixture was cooled to room temperature, dialyzed to remove unreacted precursors, and then freeze-dried to obtain CDs powder.

[0011] Furthermore, the molar ratio of ATMP to sodium citrate is 2:1~3.

[0012] Preferably, the reaction concentration of ATMP is 0.02~0.06 mol / L, and the reaction concentration of sodium citrate is 0.04 mol / L.

[0013] Furthermore, the precursor solution is placed in a sample vial, and the container for the high-temperature heating reaction is a high-pressure reactor with a polytetrafluoroethylene liner.

[0014] Furthermore, the high-pressure reaction temperature is 180~200℃, and the reaction time is 3.5~5 h.

[0015] Furthermore, the CDs solution cooled to room temperature was dialyzed and then freeze-dried to obtain CDs powder.

[0016] A tracer-type scale inhibitor, a fluorescent tracer-type scale inhibitor prepared by polymerizing the above-mentioned CDs with the scale inhibitor monomer acrylic acid (AA), is prepared by the following steps:

[0017] CDs were dissolved in a small amount of ultrapure water and mixed with isopropanol in a flask. The mixture was heated until the temperature stabilized, and then a mixture of isopropanol and acrylic acid solution and ammonium persulfate solution were added dropwise to initiate the polymerization reaction. After the addition was complete, the mixture was kept at this temperature for a period of time, and the isopropanol was removed by rotary evaporation. The solution was then dialyzed to remove unreacted CDs, and freeze-dried to obtain PAA@CDs powder.

[0018] In the above polymerization reaction, ammonium persulfate was used as the initiator and isopropanol was used as the chain transfer agent.

[0019] Furthermore, the mass ratio of the tracer carbon dots (CDs), acrylic acid, and chain transfer agent is 1~50:7~28:56; the mass of the initiator is 4.0% of the mass of the acrylic acid monomer.

[0020] Preferably, the CDs content is 0.25~12.5 parts, the acrylic acid content is 1.75~7 parts, the chain transfer agent content is 14 parts, and the initiator mass is 4.0% of the acrylic acid monomer mass.

[0021] Preferably, when the CDs solution is mixed with isopropanol and heated, a mixed solution of isopropanol and acrylic acid and an ammonium persulfate solution need to be added dropwise, the polymerization temperature is 80~95℃, and the polymerization time is 2~4h.

[0022] The carbon dot-based tracer scale inhibitor prepared by the above method has CDs modified on it that emit blue light. The fluorescence excitation spectrum and emission spectrum show a good mirror symmetry relationship, with the optimal excitation wavelength being 330 nm and the optimal emission wavelength being 432 nm. The particle size distribution is 0.6~1.8 nm, with an average particle size of 1.15 nm. The surface contains amino and phosphate groups, etc. The PAA@CDs surface has amino, phosphate, and carboxyl groups, etc. The CDs are uniformly distributed on the PAA to form a complex.

[0023] In the tracer process, the PAA@CDs utilize CDs as the detection material, and their concentration is detected based on the fluorescence intensity of the PAA@CDs.

[0024] Furthermore, the concentration of PAA@CDs showed a good linear relationship with its fluorescence intensity. The linear equation for fluorescence intensity F versus concentration C was F = 2.31C + 7.36, and the linear correlation coefficient R0 was [missing value]. 2 The value was 0.997, and the detection limit was 2.76 mg / L.

[0025] The present invention has the following beneficial effects:

[0026] 1. This invention synthesizes carbon dots (CDs) with strong and stable fluorescence intensity via a one-step hydrothermal method using ATMP and sodium citrate as precursors. Post-processing is performed using dialysis, which is simple and convenient. Compared to traditional fluorescent dyes, CDs exhibit excellent biocompatibility and stability. Furthermore, the small particle size of CDs gives them high surface energy, making them more prone to collision and polymerization with AA in solution.

[0027] 2. The CDs synthesized using ATMP and sodium citrate as precursors provided by this invention are further polymerized with AA via free radical polymerization to obtain PAA@CDs. PAA@CDs exhibit stable fluorescence intensity under various conditions and are environmentally friendly, thus improving the biocompatibility problem of traditional fluorescent tracer-type scale inhibitors.

[0028] 3. The blue light-emitting PAA@CDs prepared by this invention exhibit good linearity between fluorescence intensity and concentration, providing a new direction for the development of fluorescent CDs tracer water treatment agents. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1The images show the fluorescence excitation and emission spectra of CDs.

[0031] Figure 2 This is a transmission electron microscope image of CDs.

[0032] Figure 3 This is the infrared spectrum of CDs.

[0033] Figure 4 Transmission electron microscopy (TEM) image of PAA@CDs.

[0034] Figure 5 The infrared spectrum of PAA@CDs.

[0035] Figure 6 A comparison chart showing the scale inhibition effects of different PAA@CDs and PAA.

[0036] Figure 7 The fluorescence emission spectrum of PAA@CDs is shown.

[0037] Figure 8 This is a linear fit plot of the fluorescence intensity of PAA@CDs as a function of its concentration. Detailed Implementation

[0038] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] This application provides tracer carbon dots (CDs) prepared using aminotrimethylenephosphonic acid (ATMP) and sodium citrate as precursors. The preparation method includes the following steps:

[0040] Sodium citrate was dissolved in ultrapure water and sonicated to dissolve it. Then, ATMP solution was added and the mixture was shaken well. The solution was then placed in a high-pressure reactor for high-temperature reaction. After the reaction was completed, the mixture was cooled to room temperature, dialyzed to remove unreacted precursors, and then freeze-dried to obtain CDs powder.

[0041] Furthermore, the molar ratio of ATMP to sodium citrate is 2:1 to 3; for example, the molar ratio is 2:1, 1:1, 2:3, or 2:1.5.

[0042] Preferably, the reaction concentration of ATMP is 0.02~0.06 mol / L, for example, a reaction concentration of 0.02 mol / L, a reaction concentration of 0.03 mol / L, a reaction concentration of 0.04 mol / L, a reaction concentration of 0.05 mol / L, or a reaction concentration of 0.06 mol / L;

[0043] Furthermore, the high-pressure reaction temperature is 180~200℃, for example, 180℃, 190℃, 200℃ or 185℃, and the reaction time is 3.5~5 h, for example, 3.5 h, 4 h, 4.5 h or 5 h.

[0044] Furthermore, the CDs solution cooled to room temperature was dialyzed and then freeze-dried to obtain CDs powder.

[0045] For specific instructions, please refer to the following example:

[0046] Example 1

[0047] The preparation method of the tracer CDs in this embodiment includes the following steps:

[0048] Weigh 0.1032 g of sodium citrate into a sample bottle, add ultrapure water and sonicate to dissolve it. Add ATMP solution with a final concentration of 0.02 mol / L, mix well, and the solution system is 10 mL. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 180℃ for 3.5 h. After cooling to room temperature, dialyze to purify and obtain a pure CDs1 solution.

[0049] The purified CDs1 solution was used to measure its fluorescence intensity under excitation wavelengths of 280–380 nm. The excitation and emission wavelength bandwidths were both 5 nm, the scan rate was 2400 nm / min, the scan interval was 0.2 nm, the optimal excitation wavelength was 330 nm, the optimal emission wavelength was 463.8 nm, and the fluorescence intensity was 82.76 au.

[0050] Example 2

[0051] The preparation method of the tracer CDs in this embodiment includes the following steps:

[0052] Weigh 0.1032 g of sodium citrate into a sample bottle, add ultrapure water and sonicate to dissolve it. Add ATMP solution with a final concentration of 0.04 mol / L, mix well, and the solution system is 10 mL. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 200℃ for 5 h. After cooling to room temperature, dialyze to purify and obtain a pure CDs2 solution.

[0053] The purified CDs2 solution was used, and its fluorescence intensity was measured at excitation wavelengths ranging from 280 to 380 nm. Both the excitation and emission wavelength bandwidths were 5 nm, the scan rate was 2400 nm / min, and the scan interval was 0.2 nm. Figure 1 As shown, the fluorescence excitation and emission spectra exhibit good mirror symmetry, with an optimal excitation wavelength of 330 nm, an optimal emission wavelength of 432 nm, and a fluorescence intensity of 6056 au. Transmission electron microscopy and infrared spectroscopy were used for characterization, as shown... Figure 2 , Figure 3 As shown in the figure. TEM results show that the CDs particle size distribution is 0.6~1.8 nm, with an average particle size of 1.15 nm. Infrared results show that CDs contain amino, hydroxyl, carboxyl and phosphate groups.

[0054] Example 3

[0055] The preparation method of the tracer CDs in this embodiment includes the following steps:

[0056] Weigh 0.1032 g of sodium citrate into a sample bottle, add ultrapure water and sonicate to dissolve it. Add ATMP solution with a final concentration of 0.06 mol / L, mix well, and the solution system is 10 mL. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 190℃ for 4 h. After cooling to room temperature, dialyze to purify and obtain a pure CDs3 solution.

[0057] The purified CDs3 solution was used to measure its fluorescence intensity under excitation wavelengths of 280–380 nm. The excitation and emission wavelength bandwidths were both 5 nm, the scan rate was 2400 nm / min, the scan interval was 0.2 nm, the optimal excitation wavelength was 330 nm, the optimal emission wavelength was 447.8 nm, and the fluorescence intensity was 2764 au.

[0058] Example 4

[0059] Examples 4-10 are fluorescent tracer-type scale inhibitors prepared by polymerizing the above-mentioned CDs with the scale inhibitor monomer acrylic acid (AA) using a tracer-type scale inhibitor from Example 2. The preparation method includes the following steps:

[0060] CDs were dissolved in a small amount of ultrapure water and mixed with isopropanol in a flask. The mixture was heated until the temperature stabilized, and then a mixture of isopropanol and acrylic acid solution and ammonium persulfate solution were added dropwise to initiate the polymerization reaction. After the addition was complete, the mixture was kept at this temperature for a period of time, and the isopropanol was removed by rotary evaporation. The solution was then dialyzed to remove unreacted CDs, and freeze-dried to obtain PAA@CDs powder.

[0061] In the above polymerization reaction, ammonium persulfate was used as the initiator and isopropanol was used as the chain transfer agent.

[0062] Furthermore, the mass ratio of the tracer carbon dots (CDs), acrylic acid, and chain transfer agent is 1~50:7~28:56; for example, a mass ratio of 1~25:7~20:56, a mass ratio of 25~50:20~28:56, a mass ratio of 20~40:25~20:56, a mass ratio of 1:7:56, a mass ratio of 50:20:56, a mass ratio of 25:15:56, a mass ratio of 50:10:56, a mass ratio of 27:15:56, or a mass ratio of 37:14:56; the mass of the initiator is 4.0% of the mass of the acrylic acid monomer.

[0063] Preferably, the CDs content is 0.25~12.5 parts, for example, 0.25~7.5 parts, 7.5~12.5 parts, 0.25~3.5 parts, or 9.5~12.5 parts; the acrylic acid content is 1.75~7 parts, for example, 1.75~4 parts, 4~7 parts, 3~5 parts, or 2~4 parts; the chain transfer agent content is 14 parts; and the initiator mass is 4.0% of the acrylic acid monomer mass.

[0064] Preferably, when the CDs solution is mixed with isopropanol and heated, the mixed solution of isopropanol and acrylic acid and the ammonium persulfate solution need to be added dropwise. The polymerization temperature is 80~95℃, for example, 80~90℃, 90~95℃, 80~85℃ or 85~90℃, and the polymerization time is 2~4h, for example, 2~3h, 3~4h, 2.5~3.5h or 3.5~4h.

[0065] Specifically, in this embodiment, the method for preparing the tracer-type scale inhibitor PAA@CDs using the tracer CDs prepared in Example 2 includes the following steps:

[0066] 0.25 g of CDs2 (hereinafter referred to as CDs) was weighed into a flask and dissolved in ultrapure water. Isopropanol was added, and the mixture was heated to 80°C. Isopropanol was mixed with acrylic acid (7 g) to form solution A, and ammonium persulfate was used as solution B. Solutions A and B were added dropwise to the flask. After the addition was complete, the mixture was kept at this temperature for 2 h. Isopropanol was removed by rotary evaporation, and the product was further dialyzed and freeze-dried to obtain PAA@CDs-1 powder.

[0067] Example 5

[0068] The method for preparing tracer-type scale inhibitor PAA@CDs using tracer CDs prepared in Example 2 includes the following steps:

[0069] 2.5 g of CDs were weighed and dissolved in ultrapure water in a flask. Isopropanol was added, and the mixture was heated to 80°C. Isopropanol was mixed with acrylic acid (7 g) to form solution A, and ammonium persulfate was used as solution B. Solutions A and B were added dropwise to the flask. After the addition was complete, the mixture was kept at this temperature for 2 h. Isopropanol was removed by rotary evaporation, and the solution was further dialyzed and freeze-dried to obtain PAA@CDs-2 powder.

[0070] Example 6

[0071] The method for preparing tracer-type scale inhibitor PAA@CDs using tracer CDs prepared in Example 2 includes the following steps:

[0072] 12.5 g of CDs were weighed and dissolved in ultrapure water in a flask. Isopropanol was added, and the mixture was heated to 80°C. Isopropanol was mixed with acrylic acid (7 g) to form solution A, and ammonium persulfate was used as solution B. Solutions A and B were added dropwise to the flask. After the addition was complete, the mixture was kept at this temperature for 2 h. Isopropanol was removed by rotary evaporation, and the solution was further dialyzed and freeze-dried to obtain PAA@CDs-3 powder.

[0073] It was characterized by TEM and infrared spectroscopy, and the results are as follows: Figure 4 , 5 As shown in the image. TEM results show that the CDs aggregated together and were evenly distributed. Further observation revealed that the CDs were tightly aggregated, indicating that multiple CDs were bound to the PAA chain, ultimately presenting a spherical or near-spherical shape. Infrared results showed that PAA@CDs had obvious carboxyl, amino, and phosphate groups, indicating that the CDs successfully polymerized with PAA.

[0074] Example 7

[0075] The method for preparing tracer-type scale inhibitor PAA@CDs using tracer CDs prepared in Example 2 includes the following steps:

[0076] 6.25 g of CDs were weighed and dissolved in ultrapure water in a flask. Isopropanol was added, and the mixture was heated to 80°C. Isopropanol was mixed with acrylic acid (1.75 g) to form solution A, and ammonium persulfate was used as solution B. Solutions A and B were added dropwise to the flask. After the addition was complete, the mixture was kept at this temperature for 2 h. Isopropanol was removed by rotary evaporation, and the product was further dialyzed and freeze-dried to obtain PAA@CDs-4 powder.

[0077] Example 8

[0078] The method for preparing tracer-type scale inhibitor PAA@CDs using tracer CDs prepared in Example 2 includes the following steps:

[0079] 8.75 g of CDs were weighed and dissolved in ultrapure water in a flask. Isopropanol was added, and the mixture was heated to 80°C. Isopropanol was mixed with acrylic acid (1.75 g) to form solution A, and ammonium persulfate was used as solution B. Solutions A and B were added dropwise to the flask. After the addition was complete, the mixture was kept at this temperature for 2 h. Isopropanol was removed by rotary evaporation, and the product was further dialyzed and freeze-dried to obtain PAA@CDs-5 powder.

[0080] Example 9

[0081] The method for preparing tracer-type scale inhibitor PAA@CDs using tracer CDs prepared in Example 2 includes the following steps:

[0082] 8.75 g of CDs were weighed and dissolved in ultrapure water in a flask. Isopropanol was added, and the mixture was heated to 85°C. Isopropanol was mixed with acrylic acid (1.75 g) to form solution A, and ammonium persulfate was used as solution B. Solutions A and B were added dropwise to the flask. After the addition was complete, the mixture was kept at this temperature for 4 h. Isopropanol was removed by rotary evaporation, and the product was further dialyzed and freeze-dried to obtain PAA@CDs-6 powder.

[0083] Example 10

[0084] The method for preparing tracer-type scale inhibitor PAA@CDs using tracer CDs prepared in Example 2 includes the following steps:

[0085] 8.75 g of CDs were weighed and dissolved in ultrapure water in a flask. Isopropanol was added, and the mixture was heated to 90°C. Isopropanol was mixed with acrylic acid (1.75 g) to form solution A, and ammonium persulfate was used as solution B. Solutions A and B were added dropwise to the flask. After the addition was complete, the mixture was kept at this temperature for 3.5 h. Isopropanol was removed by rotary evaporation, and the product was further dialyzed and freeze-dried to obtain PAA@CDs-7 powder.

[0086] Example of implementation effect 1

[0087] The scale inhibition performance of the carbon dot-based tracer scale inhibitor prepared in this application is as follows:

[0088] Take the PAA@CDs powder from Examples 4-8, prepare an aqueous solution, and according to the "Determination of Scale Inhibition Performance of Water Treatment Agents - Carbonate Deposition Method" (GB / T 16632-2019), prepare a solution containing Ca... 2+ Concentration 0.24 g / L, HCO3 - A water sample with an ion concentration of 0.732 g / L and a PAA@CDs concentration of 200 mg / L was heated at a constant temperature for 10 h to evaluate the scale inhibition performance of calcium carbonate. The results were compared with those of commercial and synthetic PAA. Figure 6 As shown.

[0089] Depend on Figure 6It can be seen that the scale inhibition effect of synthetic PAA is comparable to that of commercial PAA, and the addition of CDs has a certain impact on the scale inhibition ability of PAA. As the CDs content increases, the overall scale inhibition effect shows a slight downward trend. Among them, the scale inhibition effect of PAA@CDs-5 is most affected.

[0090] Example of implementation effect 2

[0091] The tracer performance of the carbon dot-based tracer scale inhibitor prepared in this application is as follows:

[0092] At a concentration of 2 mg / mL, PAA@CDs-1 exhibited a fluorescence intensity of only 124.4 au at its optimal emission wavelength under 310 nm excitation. The detectable concentration of PAA@CDs gradually decreased with increasing CD doping content. At a concentration of 0.2 mg / mL, PAA@CDs-2 showed a fluorescence intensity of 122.1 au at its optimal emission wavelength under 310 nm excitation. The fluorescence intensity of PAA@CDs-3 increased with increasing concentration, reaching 21.02 au at a concentration of 10 mg / L. Figure 7 As shown, the concentration of PAA@CDs-3 exhibits a good linear relationship with its fluorescence intensity. The linear equation for fluorescence intensity F versus concentration C is F = 2.31C + 7.36, and the linear correlation coefficient R0 is [missing value]. 2 The value was 0.997, and the detection limit was 2.76 mg / L. The results are as follows: Figure 8 As shown, PAA@CDs-4 and PAA@CDs-5, at a concentration of 10 mg / L, exhibited fluorescence intensities of 30.34 au and 27.51 au, respectively, comparable to PAA@CDs-3.

[0093] Based on the combined implementation results of Examples 1 and 2, PAA@CDs-3 exhibits excellent scale inhibition and fluorescence properties, making it the best choice for CDs-based tracer PAA.

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a carbon dot-based tracer scale inhibitor, characterized in that, The steps are as follows: (1) Using ATMP and sodium citrate as precursors, tracer carbon dots CDs are synthesized by a one-step hydrothermal method, including the following steps: dissolving sodium citrate in ultrapure water, sonicating it to dissolve, then adding ATMP solution, shaking well, then placing the solution in a high-pressure reactor for high-temperature reaction, after the reaction is completed, cooling it to room temperature, dialysis to remove unreacted precursors, and freeze-drying to obtain CDs powder. (2) The carbon dot CDs tracer from step (1) are polymerized with acrylic acid by free radical polymerization to prepare carbon dot-based tracer scale inhibitor PAA@CDs, including the following steps: CDs are dissolved in a small amount of ultrapure water, mixed with isopropanol in a flask and heated. After the temperature stabilizes, a mixed solution of isopropanol and acrylic acid and ammonium persulfate solution are added dropwise to carry out the polymerization reaction. After the addition is completed, the temperature is maintained for a period of time, isopropanol is removed by rotary evaporation, the solution is dialyzed to remove unreacted CDs, and then freeze-dried to obtain PAA@CDs powder. In step (1), the molar ratio of ATMP to sodium citrate is 2:(1~3). The conditions for the one-step hydrothermal method are a temperature of 180~200℃ and a time of 3.5~5h; The conditions for the free radical polymerization method are a temperature of 80~95℃ and a time of 2~4h.

2. The method for preparing the carbon dot-based tracer scale inhibitor according to claim 1, characterized in that: The concentration of ATMP is 0.02~0.06 mol / L.

3. The method for preparing the carbon dot-based tracer scale inhibitor according to claim 2, characterized in that: The tracer carbon dots (CDs) have a particle size distribution of 0.6–1.8 nm and an average particle size of 1.15 nm. The surface contains amino and phosphate groups. The tracer carbon dots (CDs) are blue light emitting carbon dots. The fluorescence excitation spectrum and emission spectrum exhibit a good mirror symmetry relationship. The optimal excitation wavelength is 330 nm and the optimal emission wavelength is 432 nm.

4. The tracer-type scale inhibitor prepared by the method according to any one of claims 1-3, characterized in that: The tracer-type scale inhibitor is a complex formed by CDs uniformly distributed on PAA.

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